Project 3. Development of a Reverse Genetics System for New World Hantaviruses. G. Pan, Project Leader Little is known about the genes that confer pathogenicity in hantaviruses. This project will develop a true reverse genetics system for hantaviruses, to facilitate the association of protein function with specific genetic sequences. Development of this technique will also support the generation of recombinants hi Project 1. Reassortants, some of which have been already developed, will be used to explore differences in in vitro replication, with the ultimate goal of identifying markers of pathogenesis using an animal model. Specific aims are as follows: Aim 1. Subclone hantavirus (Prospect Hill, Sin Nombre, and Andes viruses) genome segments into i) a two plasmid expression system, where one plasmid contains the Pol I promoter and the other contains the HCMV MEEP, and ii) the dual expression vector pADSOO, to expressed both mRNA and vRNA hantavirus RNA from the same plasmid. Aim 2. Assay for the production of hantavirus mRNA, vRNA and proteins and screen for the generation of infectious virus. Aim 3. Use reassortant viruses to infect hamsters to access which gene function is associated with pathogenesis.